1. Field of the Invention
The present invention relates to a dustproof view finder, for example, in a lens shutter type of camera.
2. Description of Related Art
In a known lens shutter type of camera, an inverted Galilean finder or a real image type finder is used as a view finder. For instance, a known real image type view finder is comprised of a first lens group 41, a second lens group 43, a rectangular prism 45, an image erecting prism 47, and an eyepiece 49, arranged in this order from the object side, as shown in FIG. 6. The real image type view finder also includes a field plate 51 located in an aerial space defined between an emission surface of the rectangular prism 45 and an incident surface of the image erecting prism 47. The view finder is supported for example by a camera body. The field plate 51 is made of a thin transparent plate with a field frame 53 evaporated on its rear surface, as shown in FIG. 7.
The field frame 53 is immovably held by a field plate holder 56 at a predetermined position, as shown in FIG. 8. The field frame 53 and the field plate holder 56 are usually exposed to the atmosphere.
Accordingly, dust or foreign matter 52 may adhere to the field plate 51 (FIGS. 7 and 8). As is well known, the field plate 51 is located in the vicinity of an image plane formed by the first lens group 41 and the second lens group 43. Therefore, if dust (or foreign matter) 52 adheres to the field plate 51, the field of view of the finder, and accordingly the image of an object to be taken, will be obstructed.
The same is true when the field frame 55 is provided on the incident surface of the image erecting prism 47 or the vicinity thereof (FIG. 9).